The transmission of digital data along a transmission line may be accomplished using a cable driver. The cable driver receives the signal to be transmitted and generates a corresponding signal on the transmission line. One objective in the design of cable drivers is to maximize the rate at which data may be transmitted (the "data rate") on the transmission line. Among other limitations, the maximum data rate which may be transmitted will be limited by two considerations:
i. The cable driver should not generate excessive electromagnetic radiation, which may affect the operation of other devices near the cable driver. To avoid electromagnetic radiation, the 20% to 80% rise and fall time of the low to high and high to low transitions of the output signal of the cable driver must not be less than a specified minimum rise/fall time. In the case of some cable drivers used in the motion picture and television industries, the Society of Motion Picture and Television Engineering (SMPTE) has set out a minimum rise/fall time of 400 pico-seconds (See SMPTE Standard 259M: 10-Bit 4:2:2 Component and f.sub.SC Composite Digital Signal Serial Digital Interface). PA1 ii. The cable driver should minimize any jitter in its output signal by ensuring that the output signal is within a specified tolerance of its steady state level prior to the start of the next transition of the output signal.
Prior art cable drivers control the rise and fall times of the output signal with a resistor-capacitor circuit. Such circuits exhibit exponential low to high and high to low output transitions with the result that the output signal takes a relatively long time to settle within the specified tolerance to minimize jitter, while still having a sufficiently long 20% to 80% rise and fall time. Consequently, the data rate which can be transmitted by prior art cable drivers is limited.